What Happened at Gmail?

Image caching on the web and in email is controlled through headers, which are sent back with images. The header informs the web browser or email client how long and under which conditions the image should be re-used before making another request to the server. In its initial rollout in December, Gmail respected the caching headers sent from the original server, but always served images to the user with instructions to re-use the same image for 24 hours.

Due to the 24-hour caching header, web browsers would see real-time content initially but not on subsequent re-opens until one day later. Since open tracking also relies on images, the initial opens registered properly but re-opens were cached and could not be tracked. There were some reported workarounds for re-open tracking, but they involved sending malformed data to the Gmail proxy and were not guaranteed to work.

The Return of Real-Time Content and Re-Open Tracking

Last week, the Movable Ink team noticed that Gmail had begun deploying updates to address the issues caused by its 24-hour caching. The cache still exists, but it is now overridable if you pass a no-cache header (example below).

This means that re-open tracking now works as it did before December’s changes. In addition, these changes fix a long-standing issue of Gmail temporarily caching entire emails when navigating between emails in Gmail. When using Movable Ink, these updates mean that whenever you open an email in Gmail, you can be sure that you are seeing the most up-to-date, real-time content on every open and re-open.

Last week, Gmail implemented changes that impact the way the email service renders images that will impact real-time content for a segment of Gmail users.

Below, we hope to clarify the Gmail changes, summarize their impact, and share what actions Movable Ink has taken and is continuing to pursue to address any concerns.

1. What changes were made in Gmail, and what is the impact to Movable Ink?Traditionally, when a recipient views an email, images are downloaded from the server that hosts the images. This allows information to be communicated back to the image’s host source—such as the user’s current location, device, and time of day.

a.) Gmail is now requesting all images from proxy servers (googleusercontent.com), which incorrectly situates users in its headquarters in Mountain View, California when images are downloaded. This impacts the ability to geo-target image content for those Gmail users who are affected by the changes. (Note: Local Maps using zip codes appended as query parameters are unaffected.)

b.) Gmail is stripping the user-agent headers from the client request, which eliminates the ability to determine the Gmail user’s device and target image content appropriately.

c.) Gmail is removing the cache-control headers from the responses, which forces the user’s images to be stored in their browser’s cache for up to a day. This only impacts live image content if a Gmail user re-opens the email after the first open.

In summary, a limited set of Movable Ink features will not work within a segment of Gmail accounts and, in those cases, will be replaced with default content.

2. What email users are affected by the changes? How big is the impact to my list?After analyzing our data since the changes were implemented late last week, 2% – 5% of the average enterprise B2C email marketer’s subscriber list is affected by Gmail’s changes, since they only affect recipients that open emails through the Gmail.com desktop client, the Android Gmail app, and the iOS Gmail app.

Not all Gmail users are impacted.

The changes have no impact on Gmail users who access their accounts through Mac Mail, the native Mail app on iOS devices, non-Gmail Android apps, non-Gmail Windows apps, Gmail via Outlook, etc. Additionally, all email domains that are not @gmail.com are not impacted. (Update: As of 12/12, Gmail has rolled out the changes to custom domains as well.)

More Gmail recipients open email on iOS devices (iPhones and iPads) than through any other email service — including web-based Gmail itself, which greatly mitigates the impact of the changes, and is the reason why they only affect 2% – 5% of most email marketers’ subscribers.

Below is a summary of who is affected by the changes:

3. How is Movable Ink responding to the affected features?a.) Geo-targeting: We have made it possible for marketers to show default content to users that have images hosted within the Gmail proxy domain. This eliminates any concerns about displaying incorrectly geo-targeted content when a user is falsely identified as being in Mountain View, California.

b.) Device targeting: If a user’s device cannot be detected for any reason, a default version of an email will be rendered and is configurable within the Movable Ink dashboard.

c.) All other real-time content: Other types of real-time content such as countdown timers, social feeds, web crops, and video will appear as intended on the first open of an email. Subsequent opens from an individual recipient will display the original image due to Google’s caching which can last for up to a day.

Our team is in contact with representatives at Google to recommend and discuss alternatives to last week’s changes. We will be sure to share updates as we have more information. If you have any questions in the meantime, please do not hesitate to reach out to us at contact@movableink.com.